1. Lesson Title: Singulation Dale R. Thompson Computer Science and Computer Engineering Dept. University of Arkansas http://rfidsecurity.uark.edu 1 This material is based upon work supported by the National Science Foundation under Grant No. DUE-0736741. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF). Copyright © 2008 by Dale R. Thompson {d.r.thompson@ieee.org}

2. Singulation Singulation is the process that a reader performs to identify and/or communicate with a particular tag in the presence of multiple tags that are in range of the reader. http://rfidsecurity.uark.edu 2

3. Anti-collision Algorithm/Protocol An anti-collision protocol is the protocol used to prevent two or more devices from interfering with each other in a common communication channel to share the medium. They are also called medium access control (MAC) protocols. http://rfidsecurity.uark.edu 3

4. Time division multiplexing (TDM) http://rfidsecurity.uark.edu 4

5. Frequency division multiplexing (FDM) http://rfidsecurity.uark.edu 5

6. Polling http://rfidsecurity.uark.edu 6

7. Random access http://rfidsecurity.uark.edu 7

8. Pure Aloha http://rfidsecurity.uark.edu 8

9. Pure Aloha Efficiency http://rfidsecurity.uark.edu 9

10. Slotted Aloha http://rfidsecurity.uark.edu 10

11. Slotted Aloha Efficiency http://rfidsecurity.uark.edu 11

12. Pure Aloha vs Slotted Aloha http://rfidsecurity.uark.edu 12

13. Questions What is the difference between pure and slotted Aloha? Which is more efficient, pure or slotted Aloha? http://rfidsecurity.uark.edu 13

14. Framed slotted Aloha http://rfidsecurity.uark.edu 14

15. Framed slotted Aloha Efficiency http://rfidsecurity.uark.edu 15

16. Questions What is the difference between slotted Aloha and framed slotted Aloha? http://rfidsecurity.uark.edu 16

17. Gen-2 Anti-Collision Protocol (media access control) Select phase – Single out particular tag population with one or more bits with query tree protocol Inventory phase – identify individual tag using Q protocol (slotted-aloha based) – Reader sends Query with parameter Q and Session number (Q=4 is suggested default) – Reader creates slotted time – Tags pick random 16-bit number for handle – Tags in requested session pick a random number in the range [0,2^Q-1] for slot_number – If slot_number = 0, backscatter handle – If slot_number != 0, wait that number of slots to backscatter handle – Reader ACKs individual tag with handle and goes to access phase. All other tags wait. – If more that one tag answers, reader can send same Q again or send modified Q Access phase – Reader interacts with tags requesting EPC number and any other information http://rfidsecurity.uark.edu 17

18. Gen-2 Select (Query Tree) http://rfidsecurity.uark.edu 18 Time slice012345 Reader-to-Tag 0** 00* 01* Tag-to-Reader collision no answer collision Tag1 (ID = 010) 010 Tag2 (ID = 011) 011 Tag3 (ID = 100) Time slice67891011 Reader-to-Tag010 011 1** Tag-to-Reader 010 011 100 Tag1 (ID = 010) 010 Tag2 (ID = 011) 011 Tag3 (ID = 100) 100

19. Gen-2 Select (Query Tree) http://rfidsecurity.uark.edu 19

20. Gen-2 Inventory (Q protocol, form of slotted Aloha) http://rfidsecurity.uark.edu 20 Time slice012345 67 Slot number 0123 Reader-to-Tag Query Q=2 ACK handle1 Tag-to-Reader handle1collisionempty EPC1 Tag1 slot=0handle1 EPC1 Tag2 slot=1 handle2 Tag3 slot=1 handle3 Time slice89101112131415 Slot number 0123 Reader-to-TagQueryAdjust ACK handle2 Tag-to-Reader emptyhandle2emptyhandle3 EPC2 Tag1 (ID = 010) wait Tag2 (ID = 011) slot=1 handle2 EPC2 Tag3 (ID = 100) slot=3 handle3

21. Q-protocol efficiency http://rfidsecurity.uark.edu 21

22. Question What is the relationship between Q and the number of users? http://rfidsecurity.uark.edu 22

23. Contact Information Dale R. Thompson, Ph.D., P.E. Associate Professor Computer Science and Computer Engineering Dept. JBHT – CSCE 504 1 University of Arkansas Fayetteville, Arkansas 72701-1201 Phone: +1 (479) 575-5090 FAX: +1 (479) 575-5339 E-mail: d.r.thompson@ieee.org WWW: http://comp.uark.edu/~drt/ http://rfidsecurity.uark.edu 23

24. Copyright Notice, Acknowledgment, and Liability Release Copyright Notice – This material is Copyright © 2008 by Dale R. Thompson. It may be freely redistributed in its entirety provided that this copyright notice is not removed. It may not be sold for profit or incorporated in commercial documents without the written permission of the copyright holder. Acknowledgment – These materials were developed through a grant from the National Science Foundation at the University of Arkansas. Any opinions, findings, and recommendations or conclusions expressed in these materials are those of the author(s) and do not necessarily reflect those of the National Science Foundation or the University of Arkansas. Liability Release – The curriculum activities and lessons have been designed to be safe and engaging learning experiences and have been field-tested with university students. However, due to the numerous variables that exist, the author(s) does not assume any liability for the use of this product. These curriculum activities and lessons are provided as is without any express or implied warranty. The user is responsible and liable for following all stated and generally accepted safety guidelines and practices. http://rfidsecurity.uark.edu 24